This project is aimed at elucidating details regarding the manner in which components of complex (i.e., multiple-frequency) tones interact to produce responses in single auditory nerve fibers of cats. The major thrusts are (a) to study the "two-tone suppression" phenomenon and (b) to develop a computational scheme which utilizes descriptions of discharge rate, discharge synchronization and suppression behavior of tonal components as its input and provides quantitative estimates of overall discharge rate and time structure as its output. Specific studies for this, the third and final funded year, include examination of (1) suppression behavior when the suppressor consists of a band of noise rather than a tone, (b) the additivity of suppression, (c) the "physiological vulnerability" of suppression, (d) the comparison of forward-masking and simultaneous-masking measures of suppression magnitude, and (e) the testing of a newly-developed technique for predicting response behavior to complex tones.